Two stage hydroprocessing with divided wall column fractionator

Abstract

A divided wall column allows for fractionation of multiple streams while maintaining separate product qualities. Effluents from multiple stages of a reaction system can be processed in a single divided wall column. The divided wall column can produce multiple cuts from each separated area, as well as at least one output from a common area.

What is claimed is: 
     
       1. A method for producing low sulfur distillate products, comprising:
 hydrotreating a feedstock under first effective hydrotreating conditions to produce a hydrotreated feedstock that comprises a diesel product fraction having a sulfur content of about 15 wppm to about 50 wppm; 
 fractionating the hydrotreated feedstock in a first volume of a divided wall column fractionator to produce at least a first diesel product fraction, a first bottoms fraction, and a first common fraction that is passed to an upper undivided volume of the fractionator; 
 hydroprocessing a portion of the first bottoms fraction under effective hydroprocessing conditions; and 
 fractionating the hydroprocessed first bottoms fraction in a second volume of the divided wall column fractionator to produce at least a second diesel product fraction with at least one improved property relative to the first diesel product fraction, a third product fraction with at least one improved property relative to the first bottoms fraction, and a second common fraction that is passed to the upper undivided volume of the fractionator, 
 in which the second diesel fraction and the third fraction are not recycled to the hydroprocessing. 
 
     
     
       2. The method of  claim 1 , wherein the effective hydrotreating conditions include an LHSV from about 0.3 hr-1 to about 5.0 hr-1, a total pressure from about 500 psig (about 3.4 MPag) to about 3000 psig (about 20.7 MPag), and a temperature from about 650° F. (about 343° C.) to about 800° F. (about 427° C.). 
     
     
       3. The method of  claim 2 , wherein the effective hydrotreating conditions include a treat gas rate that provides an amount of hydrogen from about two times to about five times the hydrogen consumed during the hydrotreating. 
     
     
       4. The method of  claim 1 , further comprising hydrocracking the hydrotreated feed under effective hydrocracking conditions prior to passing the hydrotreated feed to the first volume of the divided wall column, the effective hydrocracking conditions comprising a temperature from about 200° C. to about 450° C., a hydrogen pressure from about 5 barg (about 0.5 MPag) to about 300 barg (about 30 MPag), an LHSV from about 0.05 hr-1 to about 10 hr-1, and a hydrogen treat gas rate from about two times to about fifteen times the hydrogen consumed during the hydrocracking. 
     
     
       5. The method of  claim 1 , wherein the effective hydroprocessing conditions comprise effective hydrocracking conditions. 
     
     
       6. The method of  claim 1 , wherein the sulfur content of the second product diesel fraction is lower than the sulfur content of the first diesel product fraction, and wherein the sulfur content of the third product fraction is lower than the sulfur content of the first bottoms fraction. 
     
     
       7. The method of  claim 1 , wherein the height of the dividing wall is selected so that the second diesel product fraction contains about 1 wt % or less of material corresponding to the first diesel product fraction. 
     
     
       8. A method for producing low sulfur distillate products, comprising:
 hydrotreating a feedstock under effective hydrotreating conditions to produce a hydrotreated feedstock having a sulfur content of about 50 wppm or less; 
 fractionating the hydrotreated feedstock in a first volume of a divided wall column fractionator to produce at least a first diesel fraction and a first bottoms fraction; 
 dewaxing a portion of the first bottoms fraction in the presence of a dewaxing catalyst under effective catalytic dewaxing conditions; 
 and fractionating the dewaxed bottoms fraction in a second volume of the divided wall column fractionator to produce at least a second diesel fraction with at least one improved cold flow property relative to the first diesel fraction and a second bottoms fraction with at least one improved cold flow property relative to the first bottoms fraction; 
 in which the second diesel fraction and the second bottoms fraction are not recycled to the dewaxing stage. 
 
     
     
       9. The method of  claim 8 , wherein the dewaxing catalyst comprises a 10-membered ring 1-D molecular sieve. 
     
     
       10. The method of  claim 8 , further comprising hydrofinishing the dewaxed bottoms fraction under effective hydrofinishing conditions prior to fractionating the dewaxed bottoms, the effective hydrofinishing conditions including a temperature from about 125° C. to about 425° C., a total pressure from about 500 psig (about 3.4 MPag) to about 3000 psig (about 20.7 MPag), an LHSV from about 0.1 hr-1 to about 5 hr-1, and a hydrogen treat gas rate from about two times to about five times the hydrogen consumed during the hydrofinishing. 
     
     
       11. The method of  claim 8 , wherein the effective catalytic dewaxing conditions include a temperature from about 280° C. to about 380° C., a pressure from about 300 psig (about 2.1 MPag) to about 3000 psig (about 20.7 MPag), an LHSV from about 0.1 hr-1 to about 5.0 hr-1, and a hydrogen treat gas rate from about two times to about fifteen times the hydrogen consumed during the dewaxing. 
     
     
       12. The method of  claim 8 , wherein the cloud point of the second diesel fraction is at least about 10° C. less than the cloud point of the first diesel fraction. 
     
     
       13. The method of  claim 8 , wherein the sulfur content of the first diesel fraction is at least about 25-wppm. 
     
     
       14. The method of  claim 8 , wherein the pour point of the second bottoms fraction is at least about 10° C. less than the pour point of the first bottoms fraction. 
     
     
       15. The method of  claim 8 , wherein the effective hydrotreating conditions include an LHSV from about 0.3 hr-1 to 5.0 hr-1, a total pressure from about 500 psig (about 3.4 MPag) to about 3000 psig (about 20.7 MPag), a temperature from about 650° F. (about 343° C.) to about 800° F. (about 427° C.), and a hydrogen treat gas rate from about two times to about five times the hydrogen consumed during the hydrotreating. 
     
     
       16. A method for producing low sulfur distillate products, comprising:
 hydrotreating a feedstock under effective hydrotreating conditions; 
 hydrocracking the hydrotreated feedstock under first effective hydrocracking conditions including a temperature from about 200° C. to about 450° C., a hydrogen pressure from about 5 barg (about 0.5 MPag to about 300 barg (about 30 MPag), 
 an LHSV from about 0.05 hr-1 to about 10 hr-1, and a hydrogen treat gas rate from about two times to about fifteen times the hydrogen consumed during the hydrocracking; 
 fractionating the hydrocracked feedstock in a first volume of a divided wall column fractionator to produce at least a first diesel fraction and a first bottoms fraction; 
 hydrocracking, without recycle, a portion of the first bottoms fraction, under effective hydrocracking conditions; and 
 fractionating the hydrocracked first bottoms fraction in a second volume of the divided wall column fractionator to produce at least a second diesel fraction and a second bottoms fraction, 
 wherein the second diesel fraction has at least one improved cold flow property relative to the first diesel fraction, and wherein the second bottoms fraction has at least one improved cold flow property relative to the first bottoms fraction and the second diesel fraction and the second bottoms fraction are not recycled to the first or second hydrocracking step. 
 
     
     
       17. The method of  claim 16 , wherein the second effective hydrocracking conditions include a temperature from about 200° C. to about 450° C., a hydrogen pressure from about 5 barg [about 0.5 MPag] to about 300 barg [about 30 MPag], an LHSV from about 0.05 hr-1 to about 10 hr-1, and a hydrogen treat gas rate from about two times to about fifteen times the hydrogen consumed during the hydrocracking. 
     
     
       18. The method of  claim 16 , further comprising hydroprocessing the portion of the bottoms fraction either before or after hydrocracking the portion of the bottoms fraction, wherein the hydroprocessing consists essentially of hydrotreating, dewaxing, and/or hydrofinishing the portion of the bottoms fraction. 
     
     
       19. The method of  claim 13  in which the sulfur content of the second diesel fraction is about 15 wppm or less.